Check valves have long been used to allow a substantially free flow of fluids in one direction while preventing flow in the other direction. Many times damping devices have been connected to the moving valve member to ease or slow the movement of the valve member and particularly to avoid slam closing of the valve member on the valve seat.
In such prior devices, difficulty has been encountered in providing seals for the shafts extending to the damping devices on the exterior of the valve body. Also, to balance pressure on some of the damping devices exterior connections were provided. The handling of back flow surges with prior damped check valves resulted in valve movement.